An air bag assembly usually comprises an air bag structure housed within a container. The air bag is typically stored in the container in a folded state. The air bag is inflated by a gas or fluid ejected by a gas generator or inflator that is in close proximity to the container.
After a vehicle collision begins, the gas generator is actuated so that an inert, non-toxic gas such as nitrogen is directed into the air bag structure. The gas is fed into the air bag structure through an air bag inlet. Upon inflation of the air bag structure, the container, which is typically mounted in a part of the instrument panel or steering wheel column, is broken and the air bag structure inflates so that the vehicle passenger is protected from injury.
A known type of air bag structure is referred to as a "bag-within-a-bag" structure. This type of structure, typically, comprises an inner bag disposed within an outer bag. The inner bag usually receives gas from the gas generator, and, subsequently, directs the gas into the outer bag so that the outer bag inflates to its necessary configuration to protect the passenger.
Various types of bag-within-a-bag air bag structures have been disclosed in the art. For example, U.S. Pat. No. 3,473,824 discloses an inner bag that ruptures so that an outer bag can be filled to protect the occupant of the vehicle during a collision. Because the bag is ruptured at some point during inflation, it is difficult to control the manner in which the outer air bag is expanded.
Another bag-within-a-bag type air bag structure has been disclosed by U.S. Pat. No. 5,249,824. This patent discloses an inner bag of a bag-within-a-bag air bag structure with venting holes in order to control the manner in which the inner bag inflates the outer bag during a vehicle collision. The vent holes direct fluid out of the inner bag in directions which are outward (lateral) from the central axis thereof. Thus, the inner air bag is difficult to manufacture and provides only a single control device to attempt to control the gas flow into the outer air bag.
Most of the prior art discloses that the inner bag of the "bag-within-a-bag" type dual air bag structure is formed of flexible fabric material, such as nylon. The inner air bag is typically formed of the same nylon material as that of the outer air bag. Although, nylon is typically the material used for an inner air bag in a dual air bag structure, other materials have been disclosed. For example, U.S. Pat. No. 3,900,210 discloses an elastic knitted inner bag. This material absorbs kinetic energy from the fluid or the gas ejected from an inflator; this absorption results in the peak sound reduction. U.S. Pat. No. 3,814,458 discloses fiberglass as the material for the inner air bag. The fiberglass material absorbs heat and kinetic energy from the inflator fluid.
Even though the prior art discloses a bag-within-a-bag type air bag structures, the prior art fails to specifically provide an air bag device that is easy to manufacture, that includes an inner bag with a plurality of devices to control the flow of gas from the inner bag to the outer bag during inflation, and, in addition, that includes an inner air bag composed of an elastomer to provide an effective kinetic energy absorption capacity of a dual air bag structure.